1. Field of the Invention
The present invention relates to a film winding method, a film winding apparatus, and a film manufacturing apparatus for manufacturing a film from a raw web of photographic photosensitive material.
2. Description of the Related Art
Recent film winding apparatus for use in film manufacturing apparatus serve to wind a strip-like member having a small thickness ranging from 10 to 20 xcexcm and a small width, such as a xc2xd-inch or an 8-mm magnetic tape. Those film winding apparatus which cause tension variations of xc2x15% or less in the strip-like member when it is wound are now in practical use.
There have not been available any film winding apparatus which cause low tension variations in the strip-like member when it is wound if the strip-like member has a large thickness ranging from 100 to 150 xcexcm and a large width, such as a web of photographic photosensitive material.
For example, as shown in FIG. 14 of the accompanying drawings, a conventional web winding apparatus 1 comprises a drive shaft 3 having an air tube 2 disposed therein and a pair of axially spaced bearings 4, 5 fixedly mounted on the drive shaft 3. A winding core 7 for winding a web 6 therearound is rotatably mounted on the outer circumferential surfaces of the bearings 4, 5. Displacement transmitting members 9 with felt members 8 disposed on their radially outer ends are mounted on a portion of the air tube 2 which is radially aligned with the winding core 7 between the bearings 4, 5.
When compressed air is introduced into the air tube 2, the air tube 2 is radially expanded to displace the displacement transmitting members 9 radially outwardly to press and rub the felt members 8 against the inner wall surface of the winding core 7.
The conventional web winding apparatus 1 is thus arranged to utilize the torque produced when the felt members 8 are rubbed against the winding core 7 as generating a tension imparted to the web 6 when the web 6 is wound around the winding core 7.
However, the conventional web winding apparatus 1 is disadvantageous in that the generated tension is not stable, with tension variations reduced only to about xc2x115% under best conditions, and it fails to generate large tension because of its principles. The maximum tension that can be generated is about 9.8 N due to the heat generated by the apparatus, and some components tend to be deformed by the generated heat if more tension is to be generated. In addition, since the air tube 2 is mounted in the drive shaft 3 and the felt members 8 are mounted on the radially outer ends of the displacement transmitting members 9, the conventional web winding apparatus 1 is structurally complex and needs skilled workmanship for its maintenance.
In the conventional web winding apparatus 1, the bearings 4, 5 and the winding core 7 are not fixed to each other by a fixing means. Therefore, when the web 6 is wound, the winding core 7 tends to be detached from the bearings 4, 5, failing to accurately wind the web 6 around the winding core 7.
When the winding core 7 with the web 6 wound therearound is removed from the bearings 4, 5, the pressure caused by the wound web 6 is applied through the winding core 7 to the bearings 4, 5. Therefore, intensive laborious attempts are required to release the web 6 from the bearings 4, 5.
It is a general object of the present invention to provide a film winding method and a film winding apparatus which are capable of obtaining a desired tension easily and stably.
A major object of the present invention is to provide a film manufacturing apparatus which allows a winding core with a web wound therearound to be released easily.
According to the present invention, a film winding method detects in advance torque characteristics of a holder on which a winding core is fixedly mounted and which is rotated by a torque generating means upon rotation of a drive shaft. A radius of a roll of the web wound around the winding core which corresponds to a cut length of the web is detected, and a winding tension of the holder which corresponds to the radius of the roll of the wound web is calculated. A rotational speed of the drive shaft is set based on the torque characteristics in order to obtain the calculated winding tension.
When the web is wound around the winding core, a stable winding tension can reliably be obtained at all times. It is thus possible to wind various webs having different thicknesses, for example, highly accurately.
The film winding method also has the steps of setting a slip rotational speed depending on the torque characteristics of the holder, calculating the radius of the roll of the wound web using the outside diameter of the winding core, the thickness of the web, and the cut length of the web, setting an initial tension and a rate of change of the tension which correspond to the radius of the roll of the wound web, and calculating the winding tension corresponding to the initial tension and the rate of change of the tension, and adding the slip rotational speed to the winding rotational speed of the holder to set a rotational speed of the drive shaft in order to obtain the calculated winding tension. It is thus possible to wind the web highly accurately under a desired winding tension under simple control, and to effectively handle changes in the thickness of the web.
According to the present invention, an apparatus for winding a web has a plurality of winding mechanisms each having a holder rotatably mounted on a drive shaft by a torque generating means, joined members having joining grooves, and lock means for preventing a winding core from being detached from the holder when the web is wound around the winding core, the winding mechanisms being joined together as a joined array by joining members fitted in the joining grooves.
The torque generating means comprises magnets and copper sheets selectively mounted on the drive shaft and the holder. Therefore, it is possible to obtain a relatively large tension with a simple arrangement, and to wind a web of a large thickness around the winding core highly accurately.
The lock means preferably comprises stoppers for pressing the winding core outwardly of the holder and moving means for moving the stoppers in a direction to increase a pressing force applied to the winding core before the web is wound around the winding core, and moving the stoppers in a direction to reduce the pressing force applied to the winding core when the winding core with the web wound therearound is removed from the holder. Preferably, the moving means has chambers defined in the holder and having tapered bottom surfaces, the stoppers being rotatably disposed in the chambers and having portions projecting outwardly from the outer circumferential surface of the holder.
With the above arrangement, the winding core is prevented from being detached from the holder under the pressing force while the web is being wound around the winding core. After the winding of the web is finished, the winding core is rotated in a direction opposite to the direction in which the web is wound, thereby to eliminate the pressing force applied via the stoppers to the winding core outwardly of the holder, thus allowing the winding core to be released easily from the winding mechanism.
The pressing force may be applied through the stoppers to the winding core by a resilient member wound around the holder. Cushioning members pressed inwardly of the holder may be held against the outer circumferential surface of the holder by the resilient member.
A torque generated by the drive shaft may be transmitted through the stoppers to the winding core. The winding core may have a groove defined therein, the cushioning members being fitted in the groove. The holder and the winding core are thus firmly fixed to each other.
The joining members may be made of resin. If the joining members of resin are used, then the weight of the joined winding mechanisms is reduced, and unwanted noise is prevented from being produced when the winding mechanisms are in operation. Since no joining members are required to be connected to the drive shaft to join the winding mechanisms, no extra load needs to be imposed on the drive shaft, and the drive shaft is prevented from being unduly deformed.
The joined array of the winding mechanisms has bolts attached to opposite ends thereof for preventing the winding mechanisms from being detached. Even while the drive shaft is in rotation, the web can smoothly be wound without the danger of the winding mechanisms becoming detached.
An apparatus for manufacturing a film according to the present invention has a roller for taking up variations of tension of a web and detecting a value of the tension, a roller for stretching the web to remove wrinkles therefrom, a roller for positioning the center of the web, a cutting unit having blades for cutting the web into a plurality of webs, and a plurality of winding mechanisms for winding the cut webs around respective winding cores. It is possible with this arrangement to apply a stable winding tension at all times, allowing the web cut to a desired length to be wound highly accurately around the winding core, and improving a slit width accuracy and a cut surface of the web. The apparatus makes it possible to manufacture a film efficiently and highly accurately.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which preferred embodiments of the present invention are shown by way of illustrative example.